Solid state lighting devices, such as semiconductor laser devices and light emitting devices, are continuing to displace conventional incandescent sources in an increasing number of applications. There can be many advantages to using solid state lighting devices, including long lifetime, colour purity and energy efficiency, but in some applications the optical power of a single solid state light source device can be insufficient to directly replace the incumbent technology. In applications where it is necessary to have a higher radiant power than a single solid state light source device can deliver, multiple devices can be combined to provide the radiant power required. Examples of such applications include projection and laser machining.
Such applications require the beam from multiple solid state light sources to be combined to create a very high light intensity spot while maintaining a small footprint. This may be to create a very high power density on a surface to generate heat, or in order to preserve optical efficiency by reducing the beam cross section, for example when undergoing a light conversion process in a scattering medium. This creates another technical challenge that comes with the use of multiple solid state light sources; combining multiple devices needs to be done judiciously in order to achieve high optical efficiency within the system.
The performance characteristics of solid state lighting devices are closely linked to the temperature of the device. Because they are generally very small, they have a very high power to volume ratio, meaning that without adequate heat sinking, they can easily overheat and suffer reduced efficiency, or become damaged. This effect is particularly important for laser diodes, and technical solutions must be implemented to control the temperature of such devices.
Different applications require different radiant power systems. For example, a home theatre projector, to be used in a dark or dimly lit room, will require a lower peak brightness than a data projector, to be used in a well-lit office meeting room. Having a multiple light source system that is highly modular and can be scaled to suit the application is advantageous.
U.S. Pat. No. 9,726,329B2; Light source apparatus; Matsuo et al. issued Aug. 8, 2017; details a light source apparatus that can house a plurality of semiconductor laser elements. They are arranged in a planar format in a holding member. The holding member has holes aligned in at least a pair of rows, a thin walled section on which the holes are arranged, formed through providing at least a pair of depressions on one side, and a thick walled section provided adjacent to the thin walled section. The semiconductor laser device is disposed on the thick-walled section and the pair of terminals are exposed through holes from the other side of the holding member. A wiring substrate can be fitted inside the grooves formed by the depressions and thin and thick walled sections.
U.S. Pat. No. 9,518,725B2; Light Source Apparatus; Sasamuro et al. issued Dec. 13, 2016; describes an apparatus that arranges a first semiconductor laser device having a stem into a first holding member, and a second semiconductor laser device having a stem into a second holding member. The second holding member is placed on top of the first holding member and has a window portion through which light form the first laser device is emitted. The stem of the laser device in the first holding member overlaps with the stem of the second laser device when viewed from a light-emitting side.
U.S. Pat. No. 9,360,745B2; Light source assembly and projector having the same; Song et al. issued Jun. 7, 2016; describes a light source assembly for a projector. This comprises an arrangement whereby multiple light sources are disposed on a first body in a first plane to emit light, and a second array of light sources are disposed on a second body in a second plane, spaced apart from the first plane at a set interval and wherein the second light sources emit light between the adjacent first light sources via through holes in the first body.
The prior art describes arrangements to combine multiple light sources in fixed assemblies. U.S. Pat. Nos. 9,518,725B2 and 9,360,745B2 describe solutions to arrange multiple semiconductor laser devices in multiple holding members to create a reduced cross section of the combined beam but do not have an arrangement that allows for size variation of the assembled module, and so do not present a scalable solution.